In cases for example at a factory and the like where several mechanical moving parts are started simultaneously, then if a worker is doing maintenance on even one of these, there is an extreme danger to the worker. Therefore, in the production areas of such factories, alarm devices are located in the vicinity of each of the mechanical moving parts to thereby minimize danger to workers when several of the parts are started together. These alarm devices are simultaneously driven by a drive operation from a command post and the like which is remote from the alarm devices, immediately before starting the mechanical moving pads, so that an audible alarm is generated to warn the worker of the impending start-up.
When the place where the alarm device is driven is remote from the alarm device itself however, there is a possibility that the generation of the audible alarm cannot be verified from the alarm device drive side. This situation wherein the drive operation is executed at the alarm device drive side to generate the audible alarm and start the mechanical moving part, without verification that the audible alarm has been sounded, can be extremely dangerous to workers at the work site. From a worker safety point of view it is therefore important to first verify that the audible alarm has been generated at the site of the mechanical moving part, before mechanical startup. A monitoring apparatus which can verify from the drive side that such an audible alarm has been generated thus becomes highly desirable.
The present inventors have already proposed in Japanese unpublished Patent Application No 5-275686, a technology for monitoring the drive condition of an alarm device. This technology involves a construction wherein, when safe, a non audible frequency drive current is supplied to an audible alarm generator such as a speaker, while when there is danger, an audible frequency drive current is supplied. The drive current flow is continually monitored, and the alarm device conditions are judged to be normal when a drive current is flowing. With this system however, it is not possible to confirm that an alarm sound which can be heard by workers in the danger area has actually been generated.
In view of the abovementioned situation, it is an object of the present invention to provide a monitoring apparatus for an alarm device, which is located at an alarm device drive side remote from the alarm device, and which can verify that an audible alarm is actually generated when the alarm device is driven.